The present invention relates to polyfunctional polyisocyanate polyadducts, preferably polyurethanes and polyurethaneureas, having a specific composition and based on di- or polyisocyanates and components reactive with isocyanate groups, and to a process for their preparation. The novel polyfunctional polyisocyanate polyadducts are preferably predominantly OH-terminated and can be advantageously used industrially, inter alia, as building blocks for polyurethane preparation, for example for the preparation of finishes, coatings, adhesives, sealing compounds, casting elastomers or foams.
Products which are composed of relatively high molecular weight di- or trifunctional polyetherols or polyesterols and less than stoichiometric amounts of di- or polyisocyanates are known in the area of polyurethane polyols. Comparatively nonuniform, generally linear polyurethane polyols having high viscosities and functionalities of from 2 to 4 result. In this context, also see Becker/Braun, Kunststoff-Handbuch, Vol. 7, Polyurethane, Hanser-Verlag 1993.
WO 97/02304 describes the preparation of polyfunctional polyurethane polyols by synthesis of dendritic and hyperbranched structures by means of special protective group techniques. WO 98/52995 describes dendrimeric, highly defined polyurethanepolyols which can be prepared by means of a shell-like (generation by generation) synthesis by using isocyanates having a primary and a tertiary NCO group and dialkanolamines. However, the products are very expensive owing to the many reaction steps and the special components not obtainable industrially.
It is an object of the present invention to provide, by means of a simple process, polyfunctional polyisocyanate polyadducts whose structures can be readily adapted to the requirements of use and which, owing to their defined composition, are capable of combining advantageous properties, such as high functionality, high reactivity, low viscosity and good solubility, and a process for the preparation of these polyfunctional polyisocyanate polyadducts.
It is a further object of the present invention to provide a process which makes it possible substantially to increase the functionality of commercial, industrial di- or polyols, di- or polyamines or aminoalcohols by reaction and, if required, also to modify them with respect to the type of functional group.
We have found that these objects are achieved, according to the invention, by reacting an adduct (A) or a polyadduct (P), which is obtainable by reacting an at least trifunctional component (a1) reactive with isocyanate groups, if required as a mixture with a difunctional component (a2) reactive with isocyanate groups, with a di- or polyisocyanate (b) and has an isocyanate group and on average more than one group reactive with isocyanate, with a further component (c) reactive with isocyanate groups to give the novel, polyfunctional polyisocyanate polyadduct having a specific composition.